1. Field of the Invention
This invention pertains to semiconductor memories and particularly to non-isolated integrated injection logic (I.sup.2 L) memory cells.
2. Description of the Prior Art
Currently, several "logic circuit families" are known, and may be divided into those in unipolar (FET) and those in bipolar technology. Particularly well known are RTL (resistor-transistor logic), DTL (diode-transistor logic), TTL (transistor-transistor logic) and ECL (emitter-coupled logic) circuit families. The latest addition to the unipolar family is the I.sup.2 L (integrated injection logic).
These various circuit families have been used in logic arrays to make up digital systems, particularly digital computers which require memories. The memories have been made up of ferrite cores and semiconductor devices. An effort has also been made to employ I.sup.2 L circuits.
A chief difficulty in employing I.sup.2 L circuitry in memory applications is that I.sup.2 L circuitry is basically of a static nature and depends on current switching. Dynamic storage and transfer devices normally applied in dense memories are not available in I.sup.2 L. As a result, prior art I.sup.2 L memory elements have been gated latches resulting in relatively large memory cell areas. A more recent approach utilizing I.sup.2 L techniques is to at least partially isolate the emitters of the vertical, inverted transistors for the purpose of addressing the cell through the emitter circuit. In this technique, power must be removed from the latch when reading out. Therefore, the information within the cell is retained by its inherent capacity and sophisticated sensing circuitry is required because of the transitory nature of the read-out signal.
The instant invention utilizes I.sup.2 L circuitry in a memory, but does not require separate emitter diffusions for word select and is not dependent upon the capacitive characteristics of the circuitry for read-out, but rather continues to inject current during a read-out cycle, as well as during the write cycle. Also, the process of manufacturing a non-isolated I.sup.2 L memory is simpler than the process of manufacture required to provide separate emitter diffusions for word select.